Herbs. Stems erect, unbranched or branched from base. Inflorescences racemose or spicate; bract 1; bractlets absent. Pedicel very short or almost absent. Calyx campanulate, apex 4-lobed. Corolla bilabiate. Stamens 4, slightly exserted; anthers 2-celled, both cells fertile. Ovary 1-locular, base usually with nectar glands; parietal placentas 2. Style slender; stigma discoid. Capsule dehiscing by 2 valves. Seeds subglobose, 4 (2 or numerous).

About 5 species: China, Japan, Russia, Europe; one species in China.